1. Field of the Invention
The present invention relates to a single-facer in a corrugating machine, and more particularly to a pasting mechanism between a core paper sheet and a liner therein.
2. Description of the Prior Art
A common corrugated cardboard sheet making machine (a single-facer) in the prior art is shown in FIGS. 12, 13 and 14, and a corrugated cardboard sheet making machine provided with a pressure member in the prior art is shown in FIGS. 15 and 16. A corrugated cardboard sheet making machine employing a belt pressing system is shown in FIG. 17.
A common single-facer in the prior art corrugating machine is composed of an upper roll 1, a lower roll 2 meshed with the upper roll 1 for shaping and a core paper web 4 into a corrugated shape (for corrugating a core paper web 4) as shown in FIGS. 12, 13 and 14, a pressure roll 3 for making a pasted core paper web 4 a liner 5 pass between the lower roll 2 and the pressure roll 3 while pressing them to stick them together and thereby making a single-faced corrugated cardboard sheet 6. A pasting roll 8 is provided; and for transferring and feeding paste 7 to crest portions of corrugations of the core paper web 4 that is shaped by being pinched between the upper and lower rolls 1 and 2, and the like.
Now, in the case of sticking the core paper web 4 to the liner 5 via the paste 7 transferred to the crest portions of the corrugations, essentially an appropriate pressing force and heating of the paste 7 are necessary. Thus in a single-faced corrugated cardboard sheet making machine are assembled an initial contact pressure adjusting device between the respective engaging rolls as well as a device capable of setting the rolls 1, 2 and 3 at a high temperature by introducing steam or oil into these rolls.
Next, brief description will be made on the structure of the upper roll 1 and the lower roll 2. In FIGS. 12, 13 and 14, a lower roll 2 is pivotably supported at a fixed position via bearings not shown, which are held as pinched by a frame 9 and a bracket 10. On the other hand, an upper roll 1 is pivotably supported by an arm 12 which can swing about fulcrum pins 11 via a bearing, and the other end of the same arm 12 is connected to a pressing cylinder 14 which is swingably mounted to the bracket 10 via a pin 13. Accordingly, if the pressing cylinder 14 is operated so as to extend and contract, it is possible to engage and disengage the upper and lower rolls 1 and 2 with and from each other, and also, provision is made such that a contact pressure between the respective rolls 1 and 2 can be arbitrarily adjusted by changing a hydraulic pressure in the cylinder 14. A method for supporting the pressing roll 3 from the frame 9 is similar to the method for supporting the upper roll 1, and provision is made such that a contact pressure between the lower roll 2 and the pressing roll 3 can be arbitrarily adjusted.
However, the above-described type of machine had the following disadvantages in connection to engagement between the lower roll 2 and the pressing roll 3. That is, as shown in FIG. 13, the teeth of the upper and lower corrugating rolls 1 and 2 in the prior art are straight teeth cut on the circumferential surface of the rolls in parallel to the roll axes, and under a meshed condition the teeth would be held in line contact with each other in parallel to the roll axes. Since the pressing roll 3 is a roll having a perfectly circular cross-section, at the engaging point with the lower corrugating roll 2, the engaging portions of the respective rolls 2 and 3 would take the states shown in FIG. 14. In this figure, solid lines depict the state where the pressing roll 3 is engaged with two teeth of the corrugating roll 2, while dash-dot lines depict the state where the pressing roll 3 is engaged with a crest portion of a single tooth of the corrugating roll 2. As described above, the engaged state of the respective rolls 2 and 3 would alternately repeat the engaged states depicted by solid lines and dash-dot lines according to a relative rotation between the rolls 2 and 3, respectively, and hence the center distance between these rolls 2 and 3 would always vary within the range of the maximum distance S shown in FIG. 14. From the above-mentioned reasons, vibrations and noises caused by the vibrations would be generated at the rolls 1, 2 and 3, and in an extreme case, for instance, in the case where raw paper web of poor quality is used, cutting (breaking) of the paper web would occur as a result of impacts and vibrations between the rolls. As a result of such bad working, degradation of quality such as mechanical strength of the produced corrugated cardboard sheet 6 was inevitable. In view of the aforementioned disadvantages, in recent years, machines of the types shown in FIGS. 15, 16 and 17 have been proposed.
The machine of the type shown in FIGS. 15 and 16 is a machine disclosed in the Official Gazette of Laid-Open Japanese Patent Specification No. 53-29893 (1978), in which in lieu of the pressing roll 3 in FIG. 12, there is provided a pressing member 20 positioned on the side opposed to the lower corrugating roll 2 via the raw paper webs (core paper web and liner web) and having a curved surface with a radius of curvature equal to or larger than the radius of the lower corrugating roll 2. In this structure, the gap clearance between the pressing member 20 and the lower corrugating roll 2 does not vary from an engaging point A up to an engaging point B shown in FIG. 16, and generation of vibrations and noises can be prevented. However, because of the fact that this pressing member 20 has a curved surface of a length longer than an intertooth distance l of the lower corrugating roll 2 and has its position fixed, in the course of traveling from the engaging point A up to the point B, a frictional force generated between the liner 5 and the pressing member 20 acts upon the liner 5. Accordingly, there is a shortcoming that a velocity difference is produced between the core paper web 4 forced to travel and the liner 5 subjected to a braking force, and hence peeling or poor sticking would occur.
Next, the machine of the type shown in FIG. 17 is a machine disclosed in the Official Gazette of Laid-Open Japanese Utility Model Specification No. 52-168769 (1977), in which the pressing member 20 in FIGS. 15 and 16 is omitted, and instead there are provided an endless belt 15 and an electromagnetic wave transmitter 21 disposed in the proximity of the inside or the outside of the endless belt 15 and capable of being set at a predetermined frequency. The electromagnetic wave transmitter 21 functions to apply an electric field to the lower corrugating roll 2 to enhance an adhesive force by gelling starch paste and also to dry the single-faced corrugated cardboard sheet 6 in the course of traveling. In other words, the corrugated cardboard sheet making machine of the belt-pressing type shown in FIG. 17 cannot apply a pressing force necessitated upon sticking the core paper web 4 and the liner 5 to each other in view of a property (a rupture resistance) of the belt 15, but it can provide the function of a single-facer only when it was assisted by the auxiliary function of the electromagnetic wave transmitter 21. Accordingly, although vibrations and noises which were shortcomings of the pressing-roll type could be eliminated, in the manufacture of a single-faced corrugated cardboard making machine, increased cost was inevitable.
In summary, the prior art described above involved the following problems to be resolved:
(1) The common corrugated cardboard sheet making machine in the prior art illustrated in FIGS. 12, 13 and 14 is of such type that at the time of sticking a core paper web formed in a wave-shape by means of upper and lower corrugating rolls to a liner via paste, a necessary pressing force is applied by a pressing roll held in contact with the corrugating roll via the core paper web and the liner, in which vibrations and noises would be generated by variations of a center distance between the corrugating roll and the pressing roll caused by changes of the relative phase between the respective rolls, that is, by the fact that the pressing roll alternately engages with the crest portion of the tooth of the corrugating roll and the middle portion (valley portion) between the teeth thereof. In addition, due to these vibrations, in the event that a core paper web of poor quality is used, there is a fear of breaking of the paper web, and so, degradation of quality of the product is inevitable. PA0 (2) In the machine of the type shown in FIGS. 15 and 16, a difference in a traveling velocity is produced between the core paper web and the liner due to a slide resistance of the pressing member, hence there is a fear that peeling and imperfect sticking condition may be created, and it results in degradation of quality of the product (formation of unacceptable products). PA0 (3) In addition, the machine of the type shown in FIG. 17 raises a manufacturing cost of a single-faced corrugated cardboard sheet making machine, jointly with a control apparatus, because it necessitates a special device such as an electromagnetic wave transmitter and the like.